Stilbenes are biologically active phenolic compounds exhibiting a broad spectrum of antibiotic and pharmacological activities, and plants modified with respect to stilbene content may useful for various purposes. Diverse plants and plant families naturally produce stilbenes, including grape (Vitaceae), Scots pine (Cyperaceae), tall fescue (Poaceae), and peanut (Arachaceae) (Sotheeswaran, S. and Pasupathy, V. 1993. “Distribution of resveratrol oligomers in plants,” Phytochemistry 32:1083-1092; Powell, et al. 1994. “Isolation of resveratrol from Festuca versuta and evidence of the widespread occurrence of this stilbene in the Poaceae,” Phytochemisty 35:335-338; Ingram, J. L. 1976. “3,5,4′-Trihydroxystilbene as a phytoalexin from groundnut (Arachis hypogaea). Phytochemistry 15,1791-1793).
Stilbenes have been reported to play a role in plant resistance to fungal pathogens. Constitutive stilbene accumulation is believed to function as a mechanism of general resistance to microbial pathogens, while in some plants, stilbenes accumulate as phytoalexins in response to microbial attack.
Further, stilbenes are thought to have health-promoting effects, and plants containing stilbenes may be desirable in human and animal diets. Stilbenes have been shown to have a number of beneficial effects on human health, based on epidemiological studies and laboratory studies involving humans, animals, cell cultures and enzyme assays (Jang, et al. 1997. “Cancer chemopreventative activity of resveratrol, a natural product derived from grapes,” Science 275:218-220).
Of particular interest is the stilbene resveratrol. Resveratrol is present in wine and may be involved in the health-promotive effects of moderate wine consumption. The increased consumption of resveratrol has been proposed as a way to reduce cancer rates and coronary heart disease in humans (Soleas, et al. 1997. “Wine as a biological fluid: history, production, and role in disease prevention,” J Clin Lab Anal 11: 287-313). Resveratrol and plant extracts containing resveratrol have been shown to be effective in prevention and therapy of atherosclerosis (Arichi, et al. 1982. Chem Pharm Bull 30:1766), as an anti-inflammatory agent (Kimura, et al. 1985. Biochem Biophys Acta 834:275), and as an anti-hyperoxidative agent (Kimura, et al. 1983. Plant Med J Med Plant Res 49:51). Resveratrol showed significant inhibition of aberrant colon crypt formation in a carcinogen (azoxymethane) treated rat model, suggesting utility in inhibiting tumorogenesis in humans (Steele, et al. 1998. “Cancer chemoprevention drug development strategies for resveratrol,” Pharm Bio 36:62-68 suppl). Resveratrol has also been found to promote the formation of nitroxides which are effective as vasodilatory agents and in inhibiting platelet aggregation (Fitzpatrick, et al. 1993. Am J Physiol 34:774).
Resveratrol has the following chemical structure: The biosynthetic pathway of resveratrol in plants involves stilbene synthase. Resveratrol is formed when stilbene synthase converts one molecule of p-coumaroyl-CoA and three molecules of malonyl-CoA into resveratrol, i.e., 3,5,4′-trihydroxystilbene. In some plant species, resveratrol production is inducible, and resveratrol accumulates as a phytoalexin following microbial attack (Langcake, P. and Pryce, R. J. 1976. “The production of resveratrol by Vitis vinifera and other members of the Vitaceae as a response to infection or injury,” Physiol Plant Pathol 9:77-86; Dercks, et al. 1995. “Stilbene phytoalexins and disease resistance in Vitis.” In Handbook of Phytoalexin Metabolism and Action, M. Daniel and R. P. Purkayastha, eds, Marcel Dekker, Inc. USA, pp. 287-315).
Not all plants naturally accumulate resveratrol or other stilbenes. Heterologous accumulation of resveratrol has been achieved in plants which do not naturally accumulate resveratrol by genetic engineering to express resveratrol synthase. For example, transformation of tobacco with a resveratrol synthase (RS) genomic clone from peanut resulted in the rapid accumulation of resveratrol following treatment of cell suspension cultures with fungal elicitor (Hain, et al. 1990. “Expression of a stilbene synthase gene in Nicotiana tobacum results in synthesis of the phytoalexin resveratrol,” Plant Mol Biol 15:325-335). Subsequent experiments with an RS gene (Vst1) from V. vinifera L. demonstrated a significant level of resistance in transgenic tobacco, tomato, and rice to fungal pathogens Botrytis cinerea, Phytophtora infestans, and Pyricularia oryzae, respectively [Hain et al. 1993. “Disease resistance results from foreign phytoalexin expression in a novel plant,” Nature 361:153-156; Thomzik, et al. 1997. “Synthesis of a grapevine phytoalexin in transgenic tomatoes (Lycopersican esculetum Mill.) conditions resistance against Phytophthora infestans,” Physiol Mol Plant Path 51:265-278; Stark-Lorenzen, et al. 1997. “Transfer of a grapevine stilbene synthase gene to rice (Oryza sativa L.),” Plant Cell Rep 16:668-673]. These reports demonstrated that accumulation of resveratrol in foreign plant species transformed with a resveratrol synthase gene provides a means by which a broad spectrum of increased resistance to fungal pathogens can be achieved in any plant. Increased resistance to fungal pathogens, in turn, results in increased crop production and reduction in the use of crop protection chemicals.
Accumulation of resveratrol has also been reported to have some negative side effects in plants. For example, Fischer, et al. reported that plants accumulating increased levels of resveratrol were rendered male sterile. Not only was the pollen destroyed, but the plants also demonstrated lower seed yields and altered flower color (Fischer, et al. 1997. “Stilbene synthase gene expression causes changes in flower colour and male sterility in tobacco, ” Plant J 11:489-498).
Resveratrol-3-O-β-D-glucopyranoside (3,4′,5-trihydroxystilbene-3-β-D-glucoside, polydatin, piceid; hereinafter referred to as “resveratrol glucoside” or “RGluc”) is a resveratrol conjugate. The chemical structure for the trans and cis isomers are given below. 
Both trans- and cis-RGluc have been isolated from nontransgenic plants, for example, grapes (Jeandet, et al. 1994. “Occurrence of a resveratrol-β-D-glucoside in wine: preliminary studies,” Vitis 33:183-184), Eucalyptus sideroxylon wood (Hillis, et al. 1974. “Polyphenols of Eucalyptus sideroxylon wood,” Phytochemistry 13:1591-1595), and Norway spruce (Alcubilla-Marin, M. 1970. “Extraction, chromatographic separation, and isolation of fungistatic substances from the inner bark of Norway spruce,” Z. Pflanzenernaehr. Bodenk. 127:64-74).
It has been reported that human benefits previously thought to be due to resveratrol are also attributable to RGluc. For example, in International Application WO 9958119, a method for preventing or treating restenosis, a medical condition characterized by recurrent stricture of a heart valve, and for preventing the recurrence or progression of coronary heart disease was provided which involves administration of an active agent comprising cis-resveratrol, trans-resveratrol a mixture thereof, or a pharmacologically acceptable salt, ester, amide, prodrug, or analog thereof. Both cis- and trans-resveratrol glucoside (RGluc) were listed among the active agents, and the patent discloses these compounds as being either naturally occurring or chemically synthesized in the laboratory.
Subsequent to the epidemiological and biochemical studies which indicated that the resveratrol in wine was at least in part providing valuable protection against cardiovascular disease, numerous labs detected high levels of RGluc in several red and white wines. In view of these findings, it was reported that RGluc likely contributes to the human health benefit of wines (Goldberg, et al. 1996. :Resveratrol glucosides are important components of commercial wines,” Am J Enolog and Viticulture 47:415-420).
The present invention describes transgenic plants and plant cells that have been modified to contain heterologous RGluc, as well as use of such plants or plant cells in manufacturing foods, nutritional supplements, animal feed supplements, nutraceuticals, and pharmaceuticals to serve as nutritional and therapeutic elements in human and animal diets.